1. Field of the Invention
This invention relates to halide glass compositions and more particularly to halozirconate glass compositions which have good properties as hosts for rare earth elements as lasting dopants. This invention also relates to optical waveguides and optical amplifier apparatus and method employing such compositions.
2. Related Art
It has long be recognised that the rare earth elements display fluorescence and this fluorescence can be utilised in the form of lasing either for the generation of optical signals or for the amplification of optical signals. Usually the lasing species is a trivalent ion of a rare earth element. In particular the trivalent ion Pr.sup.3+ constitutes a lasing species for providing radiation at 1300 nm. This property is of interest because optical telecommunications uses signals at 1300 nm and the ion Pr.sup.3+ is capable of amplifying such signals by laser action. It will be apparent that, in order to take advantage of this property, it is necessary to provide the active species in a suitable waveguiding structure, eg. a fibre waveguide.
The halide glasses have been recognised since 1978 and a wide range of compositions have been reported and their properties studied. It has been recognised that the halide glasses form good hosts for the rare earth elements as lasing species but the identification and selection of compositions having favourable properties remains difficult. In particular the prior art has failed to identify the glass compositions capable of lasing at 1300 nm with sufficient efficiency for use in telecommunications networks. This invention relates to compositions which have good properties. It is now convenient to discuss the properties of the glass required in a lasing device such as a fibre amplifier. These properties will be considered under three different headings.